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Pathology
Deficiency of anti-diuretic hormone causing free water loss.
Can be central (failure of posterior pituitary to produce ADH) or nephrogenic (failure of kidneys to respond to ADH)
Aetiology
Central: Tumour, infiltration, infection, trauma or congenital.
Nephrogenic: Drugs (e.g. Lithium, Demeclocycline, Colchicine), familial (X-
linked AVP receptor gene), CKD
Signs
Dehydration, dehydration
Symptoms
Polydipsia, polyuria, weight loss.
Investigations
Bloods: U&E (hypernatraemia) and plasma osmolarity (raised)
MSU: Urine osmolarity (low)
Imaging: MRI pituitary
Water Deprivation Test: Water restricted for 8 hours then desmopressin given
If urine concentrated after desmopressin – Cranial DI
If urine dilate after desmopressin – Nephrogenic DI
Treatment
Central: Find underlying cause and Desmopressin.
Nephrogenic: Stop offending medications
Prognosis
Life expectancy not affected if treated.
Neurological sequelae if hypernatraemia corrected rapidly)
Key Facts
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Key References
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